Ecosystem carbon isotopic discrimination in a cool-temperate deciduous forest at Asian Monsoon region: Implication from aerosol-leaf wax biomarkers

Accurate estimates of carbon isotopic discrimination (/Delta) by photosynthesis are important to evaluate the magnitude and spatial distribution of the terrestrial uptake of carbon dioxide. The temporal and regional pattern of discrimination in terrestrial biosphere has little known because it is subject to considerable uncertainty. In this study, we measured the molecular carbon isotopic composition (/delta 13C) of plant wax in aerosol in order to estimate direct mean /Delta values of ecosystem-level at less than monthly temporal resolution. We collected bulk aerosol samples from August 2003 to November 2004 during growing season at Takayama Experimental Site (36?_q8_fN, 137?_q6_fE, 1420m a.s.l.) in a cool-temperate deciduous forest in Japan. Sampling duration ranged between 10 days and 27 days. We analyzed the molecular and /delta 13C values of major wax compound classes (n-alkanols, n-alkanoic acids and n-Alkanes) in dominate species (Betula ermanii, Quercus crispula, Sasa senanensis) and in aerosols collected at the 2m-height above the ground and also measured ?A13C of bulk air above the forest canopy. Concentrations of C23-C32 n-Alkanes in aerosol collected in the forest were ranged from 0.85 ng/m3 air (average of per 10 days samples) to 1.16ng/m3 air (average of per 19 days samples) during growing season in 2003. Mean /delta 13C of n-Alkanes (C27, C29 and C31) were ranged from _|30.0 0.4?n to _|33.9 _1.8 ?n in 2003. By using the leaf wax /delta 13C, the magnitude of /Delta 13 ranged from 15.8?n to 19.5?n in 2003.